My 1998 Renault clio is over heating?

i assume you have fixed this by now, but your problem sounds like a blown head gasket. The main symptoms would be erratic overheating, slight to medium loss of coolant, visible bubbles of gas in the water reservoir on revving, and water in the oil (this forms a yellowish frothy mixture on the oil filler cap and the dipstick). All or any of these may be missing in the case of a minor gasket fault, but will eventually develop. It's dangerous to let a slight fault mature because it can quickly become a catastrophic one, maybe leading to serious engine damage.

Leonard Sanford
March 2008

Not that i know a lot about cars. If there's no lost of coolant, then it could be some blockage in the system, i would give it a good flush first (don't forget to the bleed the air out afterwards). Otherwise had to find and fix the leakage.
Good luck!!

Peter Lee
April 2007